During urine formation, the process of ____ leaves behind mostly salt water and wastes after moving most of the filtrate back into the blood.
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tubular reabsorption
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The glomerular filtration rate in humans is such that in 24 hours, approximately ____ liters of filtrate is produced.
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180
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The ____ is a capillary knot that filters fluid from the blood into the renal tubule.
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glomerulus
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____ are responsible for driving protein-free fluid out of the glomerular capillaries and into Bowman's capsule
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Starling forces
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What hormone is responsible for increasing the water permeability of the collecting duct, allowing water to flow to areas of higher solute concentration?
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Antidiuretic hormone
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____ acts on the distal convoluted tubule to cause sodium to be reabsorbed and potassium to be secreted.
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Aldosterone
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Under what conditions would excess glucose be eliminated in the urine?
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Hyperglycemia
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The kidney is both an ____ and a ____ organ
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Excretory; regulatory
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Kidneys excrete
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Excess water, waste products, and foreign materials.
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Kidneys regulate
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1. Plasma osmolarity (concentration of a solution expressed as osmoles of solute per liter of solvent)
2. Plasma volume
3. Acid-base balance
4. Electrolyte balance
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Each nephron is composed of
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A renal corpuscle and a renal tubule.
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Renal corpuscle
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Consists of a "ball" of capillaries, called the glomerulus, which is enclosed by the fluid-filled Bowman's capsule/glomerular capsule.
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Afferent arteriole
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Supplies blood to the glomerulus.
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Glomerular filtration
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Blood flows through the glomerular capillaries and protein-free plasma filters into the Bowman's capsule.
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Efferent arteriole
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Drains the glomerulus of remaining blood.
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Filtrate flows from Bowman's capsule into
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the start of the renal tubule, called the proximal convoluted tubule.
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Filtrate then flows into the
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the Loop of Henle
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Filtrate then flows into the
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Distal convoluted tubule
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Filrate then empties into the
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Collecting duct
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Finally, the filtrate flows into and collects in the
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Minor calyces
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Nephron functions that process blood into filtrate and urine
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1. Glomerular filtration - Passive, fluid passes from lumen of glomerular capillary into glomerular capsule of renal tubule.
2. Tubular reabsorption - Moves most of the filtrate into the blood, leaving salt water and wastes in the tubule. Some desirable solutes are absorbed and others move passively from the lumen into the interstitial spaces.
3. Tubular secretion - Essentially the reverse of tubular reabsorption. Process by which the kidneys can rid the blood of additional unwanted substances (creatine, ammonia)
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Reabsorbed solutes and water that move into the interstitial space between the nephrons are returned to the blood via the ____
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Peritubular capillaries
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What will happen to the glomerular capillary pressure and filtration rate if you decrease the radius of the afferent arteriole?
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Both pressure and filtration rate will decrease.
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What will happen to the glomerular capillary pressure and filtration rate if you increase the radius of the afferent arteriole?
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Both pressure and filtration rate will increase.
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What will happen to the glomerular capillary pressure and filtration rate if you decrease the radius of the efferent arteriole?
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Both pressure and filtration rate will increase.
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Activation of sympathetic nerves that innervate the kidney leads to a decreased urine production. Knowing this fact, what do you think the sympathetic nerves do to the afferent arteriole?
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Constriction
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How is this effect of the sympathetic nervous system beneficial? Could this effect become harmful if it goes on too long?
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It conserves fluids during dehydration but causes long-term build-up of wastes.
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_____ (hydrostatic and osmotic pressure gradients) drive protein-free fluid between the blood in the glomerular capillaries and the filtrate in Bowman's capsule.
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Starling forces
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What will happen to the glomerular capillary pressure and filtration rate if you increase the blood pressure in the left source beaker?
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Both will decrease
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What will happen to the filtrate pressure in Bowman's capsule (not directly measured in this experiment) and the filtration rate if you close the one-way valve between the collecting duct and the urinary bladder?
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Pressure increases, but filtration decreases.
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Judging from the results of this laboratory activity, what shoud be the effect of blood pressure on glomerular filtration?
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Increase, unless there's an obstruction.
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Persistent high blood pressure with inadequate glomerular filtration is now a frequent problem in Western cultures. Using the concepts in this activity, explain this health problem.
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Tumors, kidney stones, or narrow vessels from plaque build-up can cause inadequate glomerular filtration.
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What will happen to glomerular capillary pressure and glomerular filtration rate if both of these arteriole radii changes are implemented simultaneously with the low blood pressure condition?
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They will both increase above the baseline amount.
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How could an increased urine volume be viewed as beneficial to the body?
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Wastes are excreted in greater amounts.
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Diuretics are frequently given to people with persistent high blood pressure. Why?
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Diuretics help remove excess water and salt through excess urine volume in order to lower blood pressure.
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What will happen to the urine volume and concentration as the solute gradient in the interstitial space is increased?
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Urine volume will decrease and concentration will increase.
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From what you learned in this activity, speculate on ways that desert rats are able to concentrate their urine significantly more than humans.
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Desert rates conserve more water via increased levels of ADH.
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Judging from this activity, what would be a reasonable mechanism for diuretics?
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Decrease water permeability of the collecting duct.
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What will happen to the glucose concentration in the urinary bladder as glucose carriers are added to the proximal tubule?
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The glucose concentration will decrease.
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Why would your family physician at the turn of the twentieth century taste your urine?
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To detect glucose and thus glycosuria caused by diabetes mellitus.
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What will happen to the urine volume (compared with baseline) when aldosterone is added to the distal tubule?
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The urine volume will decrease.
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What will happen to the urine volume (compared with baseline) when ADH is added to the collecting duct?
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Urine volume will decrease dramatically.
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What will happen to the urine volume and the urine concentration (compared with baseline) in the presence of both aldosterone and ADH?
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Urine volume will decrease and concentration will increase.
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Why does ethanol consumption lead to a dramatic increase in urine production?
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It inhibits ADH production and release.
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Why do angiotensin converting enzyme (ACE) inhibitors given to people with hypertension lead to increased urine production?
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It blocks the conversion of angiotensin I to angiotensin II, leading to increased excretion of sodium.
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